What is the force exerted on the hand by the blocks?

"a karate strike hits wooden blocks, the hand undergoes an acceleration of -6500 m/s2. Medical data indicates the mass of the forearm and hand to be about 0.8 kg. What is the force exerted on the hand by the blocks?"

Originally posted by badboyben03 can someone give me the formula needed to do this problem?

"a karate strike hits wooden blocks, the hand undergoes an acceleration of -6500 m/s2. Medical data indicates the mass of the forearm and hand to be about 0.8 kg. What is the force exerted on the hand by the blocks?"